This invention relates to a power operating system for a vehicle liftgate that is pivotally attached to a vehicle roof for pivotal movement about a generally horizontal hinge axis and more particularly to a power operating system that moves a lifigate from a fully closed position to a fully open position and from an open position to a fully closed position.
Sport utility vehicles, vans and the like that are equipped with liftgates that are hinged at the top about a generally horizontal hinge axis are used by large numbers of people today. Some of these liftgates are large and heavy. Their size and weight make some liftgates difficult to open and close. Some of the liftgates are also a great distance above the ground when they are fully opened. Their height above the ground makes them very difficult for some people to close. For these and other reasons many people would like to have a power operating system for opening and closing the liftgate.
A number of different liftgate openers have been tried in recent years. Some of these liftgate openers have a single cable that opens and closes a liftgate in connection with a counterbalance system, such as gas cylinders. Liftgates with a single cable opener and closer are generally trunk lids that are lightweight and have a relatively small range of movement.
Gas cylinder output varies with temperature. This complicates power liftgate systems that rely on gas cylinders to open the liftgate. The gas cylinder or cylinders must be strong enough to open the liftgate on the coldest date (xe2x88x9240xc2x0 C.). This results in gas cylinders that increase closing resistance substantially on the hottest day (80xc2x0 C.). Therefore a very large electric motor must be used to close the liftgate.
Liftgates that have two or more gas cylinders for a counter balance system are common. These gas cylinders generally occupy a position in which their axis is substantially parallel to the liftgate so that the gas cylinders are hidden when the liftgate is closed. In this closed position the moment arm of the gas cylinders is quite small. With such systems the lift gate may move about one-third of their total travel range before the gas cylinders exert sufficient force to open a liftgate further without the application of an independent lifting force. There are even some systems in which the gas cylinders pass over center and bias a liftgate toward a closed position when the liftgate is closed. With these self-closing systems a liftgate may need to be more than one-third open before the gas cylinders will open the liftgate further.
U.S. Pat. No. 4,903,435 granted to Werner Bittmann et al Feb. 27, 1990 discloses a device for motorized opening and closing of pivotal body panels of motor vehicles comprising an actuation rod that is pivotally attached to the pivotal body panel at one end and to a slide block at the opposite end. The slide block is moved in an inclined linear track by a control cable that is moved in a closed loop by a cable drum driven by an electric motor. The Bittnann ""435 device is bulky and cumbersome and relies on gravity to fully close the pivotal body panel.
U.S. Pat. 5,588,258 granted to Kevin Wright et al Dec. 31, 1996 discloses a power operator for a pivotal closure element comprising two gas charged struts and an extendible strut adapted for extension by a cable drive. The Wright ""258 power operator opens and closes the pivotal closure element fully. However, the extendible strut and cable drive are complicated and expensive and require substantial vertical space.
U.S. Pat. No. 6,055,775 granted to Timothy Dering et al May 2, 2000 discloses a liftgate self-closing device comprising a pneumatic actuator that is pivotally attached to liftgate at one end and to a tape at the opposite end. The tape is a generally elongated belt member having a rack formed on an underside. The rack is disposed in a track and driven by a pinion gear attached to the output shaft of an electric motor. Alternatively, the tape could be an endless member. In either event, the liftgate is opened manually until an over center condition is achieved in the pneumatic actuator which then opens the liftgate automatically. The liftgate is closed by energizing the motor to drive the tape and pneumatic actuator downwardly until the liftgate is closed by gravity. The Dering device requires manual operation to open the liftgate and relies on gravity to fully close the liftgate.
U.S. Pat. No. 6,092,337 granted to Joseph Michael Johnson et at Jul. 25, 2000 discloses a vehicle liftgate power operating system having two drive units in which a segmented sector rides in a track with an end sector that is attached to the liftgate. The segmented sector is driven by a pinion gear attached to the output shaft of an electric motor. This power operating system opens and closes the liftgate fully and is satisfactory for its intended purpose. However, the drive units reduce the head room in the cargo space which may be objectionable to some users.
The object of the invention is to provide an improved vehicle liftgate power operating system.
A feature of the invention is that the vehicle liftgate power operating system can move the liftgate from a closed position to a fully opened position as well as from an open position to a fully closed position.
Another feature of the invention is that the liftgate power operating system does not diminish head room in the cargo area.
Another feature of the invention is that power operating system is compact durable and economical to manufacture.
Still another feature of the invention is that the drive unit of the liftgate power operating system has fewer parts and is less complicated than other power operating systems.
Yet another feature of the invention is that the liftgate power operating system is vertically oriented and associated with the D-pillar to minimize intrusion into the cargo area of the vehicle and into the unobstructed load width at the liftgate opening.
Still yet another feature of the invention is that the power operating system can be used in conjunction with a counterbalance system for a manual operating system without any modification in the counterbalance system.
These and other objects, features and advantages of the invention will become more apparent from the following description of a preferred embodiment taken in conjunction with the accompanying drawing.